AUSTIN (AP) — Texas’ attorney general sued the San Antonio police chief Friday for what he said are violations of the state’s immigration law targeting “sanctuary cities” and sought millions of dollars in sanctions.

The lawsuit Ken Paxton filed in state court was a rare enforcement action of Senate Bill 4, approved last year and mostly upheld by a federal appeals court.

SB4 prohibited law enforcement agencies from refusing “detainer” requests from U.S. Immigration and Customs Enforcement, doing anything to stop an officer from asking about a suspect’s immigration status or cooperating with immigration authorities.

Paxton’s lawsuit accused McManus of improperly handling a human smuggling case in December 2017 in which 12 immigrants were found inside a tractor-trailer.

ICE typically prosecutes major cases of human smuggling, which occur frequently in South Texas due to the proximity of the U.S.-Mexico border. But in this case, McManus repeatedly declined the help of an ICE officer, instead having the driver charged with a state crime and releasing the migrants to Catholic Charities.

He also contacted the legal group RAICES, which worked with the migrants to obtain visas for witnesses of crimes who cooperate with law enforcement.

That infuriated top Texas Republicans who supported SB4. Paxton, who is himself under indictment for securities fraud, accused San Antonio of having “put the safety of police officers and the public at risk by defying state law.”

The city responded Friday with a statement accusing Paxton of “furthering a political agenda.”

San Antonio changed how it deals with human smuggling cases after a July 2017 incident in which 10 people died after riding inside a packed trailer that made it through a U.S. Customs and Border Protection checkpoint. More than 20 migrants were detained as material witnesses. Some were ultimately deported.

Police policy now says that officers “will not refer” migrants to ICE unless the person has a federal deportation warrant, and that the department along with other groups will assist victims and witnesses with getting visas.

Paxton’s lawsuit asks a judge to prohibit San Antonio from enforcing that policy of committing “future violations of SB4.” It also demands civil penalties of at least $25,500 a day for every day after Sept. 1, 2017, when the city policy took effect. That alone would surpass $11.5 million, and the lawsuit also demands other civil penalties.

City spokesman Jeff Coyle said federal officials had been consulted on its process for handling human smuggling cases.

“The City has a long history of cooperating with federal authorities and we will continue to do so,” Coyle said.